Oxygenate-to-olefin processes are well described in the art. Typically, oxygenate-to-olefin processes are used to produce predominantly ethylene and propylene. An example of such an oxygenate-to-olefin process is described in US Patent Application Publication No. 2011/112344, which is herein incorporated by reference. The publication describes a process for the preparation of an olefin product comprising ethylene and/or propylene, comprising a step of converting an oxygenate feedstock in an oxygenate-to-olefins conversion system, comprising a reaction zone in which an oxygenate feedstock is contacted with an oxygenate conversion catalyst under oxygenate conversion conditions, to obtain a conversion effluent comprising ethylene and/or propylene.
The publication further describes possible integration with a cracker. The publication also describes partially hydrogenating a C4 portion of the conversion effluent and/or cracker effluent and recycling at least part of the at least partially hydrogenated C4 as recycle feedstock to the cracker or oxygenate-to-olefins conversion system.
While the above process is useful, it would be advantageous to produce other chemical components in an oxygenate-to-olefins process. For example, the xylene isomers are valuable chemical intermediates. Ortho-xylene can be oxidized to make phthalic anhydride which can be used to make phthalate plasticizers. Meta-xylene can be oxidized to make isophthalic acid which can be used in unsaturated polyester resins. Para-xylene can be oxidized to make terephthalic acid which is used to make polymers such as polyethylene terephthalate (PET) which is one of the largest volume polymers in the world.